Spiral terminal and method of manufacturing the same

ABSTRACT

Provided is a minute spiral terminal for attaining electrical continuity with an electrode of electronic equipment or inspection equipment. The spiral terminal includes a columnar spiral spring and a protrusion protruding outward at the center of the spiral of the spiral spring. The protrusion has a contact surface to be in contact with the electrode, and the shape of the contact surface is a part of a spherical surface or a part of paraboloid of revolution.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spiral terminal used for attainingelectrical continuity with an electrode of electronic equipment havingan IC or LSI or the like by pressing the spiral terminal onto theelectrode. The invention also relates to inspection equipment andelectronic equipment which are equipped with such spiral terminal.

2. Description of the Background Art

An inspection socket is used for taking out electrical signals fromelectrodes of electronic equipment consisting of an IC or LSI throughcontact buttons by pressing the contact buttons onto the electrodes inorder to inspect the electrical continuity of the electronic equipment.A connector for packaging is used for the purpose of maintainingelectrical continuity with electronic equipment such that contactbuttons are pressed on the land electrodes of the electronic equipmentso as to maintain electrical continuity with the electronic equipmentthrough the contact buttons. The inspection socket and the connector forpackaging are provided with a number of contact buttons corresponding tothe number of the electrodes of the electronic equipment to beconnected, and higher density corresponding to high density ofelectrodes provided in electronic equipment is demanded of the contactbuttons to be provided in the inspection socket and the connector forpackaging.

One of such known contact buttons is, for example, a contact button forBGA (ball grid array). The contact button has a planar spiral shapebefore contacting a ball electrode, and the spiral shape of the contactbutton changes corresponding to the shape of the ball electrode as aresult of contact with the ball electrode (see Japanese PatentApplication Publication No. 2002-175859). It is described therein thatthis contact button can comply with high density of electrodes, securingelectrical continuity in compliance with the shape of the ballelectrode, and being highly reliable.

A known spiral terminal used for inspection is, for example, acone-shaped terminal having a spiral spring whose protrusion increasesgradually from the outer periphery to the center (see Japanese PatentApplication Publication No. 2001-235486). It is stated that when theconical probe part arranged at the tip of the cone-shaped terminal ispressed onto a plate electrode of a subject to be inspected, the conicalprobe part can surely be connected to the plate electrode of the subjectaccording to the additive force of the spring.

These spiral terminals are manufactured by various methods, such as amechanical processing in which a plate is curled up, a method in which aplating method is combined with a lithography method that usesultraviolet radiation (UV) having a wavelength of about 200 nm, a methodusing laser, etching or punching, and the like. However, if an attemptis made to manufacture a spiral terminal by machining process such ascurling a plate, there is a limit in the miniaturization of the spiralterminal, and it is difficult to manufacture precision terminalsprecisely with satisfactory reproducibility in large quantities. Withthe lithography method using UV, or the methods using laser, etching orpunching, only spiral terminals having a thickness of about 20 μm orless can be obtained, and consequently the aspect ratio is small.

Since the aspect ratio is small, if an attempt is made to increase astroke (sag amount of a spring) in order to obtain a spiral terminalhaving high reliability of connection, the spring becomes thinner, andthe spiral terminal cannot achieve electrical continuity of a largeelectric current of equal to or more than 0.5 A. Also, because of thesmall aspect ratio, the number of spirals of the terminal becomes less,and the contact load decreases if an attempt is made to enlarge thestroke, whereas the stroke decreases if the contact load is attempted tobe increased. Therefore, only spiral terminals of low connectionreliability are obtained.

When the electrode of an object to be connected is plate-shaped, thecontact button must have a convex structure in order to attain sureconnection reliability. However, if an attempt is made to process thecontact button so as to have a convex structure after formation of aspiral spring, a special process is necessary, which results in thedegradation of productivity and the increase of manufacturing cost.Moreover, the convex formation of a minute spiral spring is not easy,and consequently the yield of the product decreases. Furthermore, with amode in which the tip of a contact button having a shape like a conehaving a pointed end is pressed onto a plate electrode of an object tobe connected, the electrode is vulnerable to damage because it is madeof a soft material such as gold or a solder. Thus, if the electrode isdamaged at the stage of inspection, the fraction defective in thesubsequent step of mounting increases, and the connection reliabilitydecreases. On the other hand, the tip of the contact button tends to bedeformed, and if it is used repeatedly for a long time, a stableelectrical connection cannot be attained.

If the pointed structure of cone is formed by machining, which is theonly practically available process, the manufacturing cost becomes highsince such machining is done piece by piece. If the pointed structure ofthe cone is formed by machining, the variations of the products becomestens of μm, which results in the variations in the height of theterminals, causing variation in the stroke and the contact load at theoccasion of contact with the electrodes, and accordingly the connectionreliability decreases.

SUMMARY OF THE INVENTION

The present invention was accomplished in view of the above-mentionedproblems, and an object of the invention is to provide a low cost andhighly reliable spiral terminal for inspection equipment or for mountingin electronic equipment.

A spiral terminal of the present invention is a minute terminal toattain electrical continuity with an electrode of electronic equipmentor inspection equipment. The spiral terminal has a columnar spiralspring and a protrusion protruding outward at the center of the spiralof the spiral spring. The protrusion has a contact surface to be incontact with an electrode, and the shape of the contact surface is apart of a spherical surface or a part of paraboloid of revolution.

The columnar spiral spring may be structured such that the outerperipheral part thereof has a hollow ring structure. The spiral terminalmay be made of nickel or nickel alloy and may have a coating layerconsisting of a precious metal or alloy of a precious metal.

A manufacturing method of the present invention is a method ofmanufacturing such a columnar spiral terminal having a spiral springstructure, and the method typically includes a step of forming a layerconsisting of metallic material in a resist structure by means ofelectroforming so as to form a columnar spiral spring, a step of forminga resist structure on the spiral spring by lithography, and a step offorming a layer consisting of metallic material in the resist structureby electroforming in order to form a protrusion protruding outward.

Another manufacturing method of the present invention may include a stepof forming a resist structure by a metal mold, a step of forming a layerconsisting of metallic material in the resist structure by means ofelectroforming so as to form a columnar spiral spring, a step of forminga resist structure on the spiral spring by lithography, and a step offorming a layer consisting of metallic material in the resist structureby electroforming in order to form a protrusion protruding outward.

Inspection equipment of the present invention may have a socket equippedwith such spiral terminals and may be used for the inspection ofsemiconductors of land grid array arrangement. On the other hand,electronic equipment of the present invention may have a connectorequipped with such spiral terminals and may be connected with landelectrodes.

The spiral terminal of the present invention exhibits high connectionreliability since it does not give a mechanical damage to an electrodeof an object to be connected and its aspect ratio is high. With amanufacturing method according to the present invention, a minutecontact button can be produced precisely with satisfactoryreproducibility and at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a perspective view of a spiral terminal of the presentinvention, and FIG. 1(b) is a sectional view of the spiral terminal ofthe present invention, taken along a longitudinal plane passing thecenter thereof.

FIG. 2(a) is a sectional view showing a spiral terminal of the presentinvention, in which a cross-section perpendicular to the longitudinaldirection is circular. FIG. 2(b) is a sectional view showing a spiralterminal having two arms of the present invention.

FIGS. 3(a)-3(d) schematically show a process of manufacturing aninspection socket of the present invention.

FIGS. 4(a)-4(j) schematically show a process of manufacturing a spiralterminal of the present invention.

FIGS. 5(a)-5(l) show another process of manufacturing a spiral terminalof the present invention.

FIGS. 6(a)-6(d) show cross-sections of various modifications of spiralterminals of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the spiral terminals of the presentinvention will be described in detail with reference to the accompanyingdrawings. In the description of the drawings, the same elements will bedenoted by the same reference symbols, and redundant description will beomitted.

(Spiral Terminal)

A typical example of a spiral terminal of the present invention is shownin FIG. 1. FIG. 1(a) is a perspective view of a spiral terminal of thepresent invention, and FIG. 1(b) is a sectional view of the spiralterminal of the present invention, showing a cross-section taken along alongitudinal plane passing the center thereof. As shown in FIGS. 1(a)and 1(b), the spiral terminal of the present invention has a columnarspiral spring 1 u and a protrusion it protruding outward at the center 1uc of the spiral spring 1 u. The protrusion it has a contact surface 1tc to be in contact with an electrode of electronic equipment orinspection equipment, and the shape of the contact surface 1 tc is apart of spherical surface or a part of paraboloid of revolution.

When a spiral terminal is pressed on an electrode of an object to beconnected, it gives the electrode a mechanical damage if it has aconically sharp pointed tip structure as in the case of a conventionalspiral terminal. However, as shown in FIG. 1, a spiral terminal of thepresent invention has a protrusion it which has a contact surface 1 tcfor contacting an electrode of an object to be connected, and thecontact surface 1 tc has a shape like a part of the spherical surface ora part of paraboloid of revolution. Therefore, the spiral terminal ofthe present invention does not damage an electrode of an object to beconnected. Thus, even with repeated use for connection, the tip of theprotrusion will not crush or vary in its height, nor will the contactsurface be deformed, and the reliability of electrical connection of thespiral terminal of the present invention will not be degraded. Thespiral terminal can maintain a constant connection with an electrodeeven if they happen to contact each other in an inclined manner.

The outer peripheral part 1 ug of the columnar spiral spring 1 upreferably has a hollow ring structure. If the outer peripheral part 1ug has a hollow ring structure, it is easy to mount the spiral terminalonto a substrate, and holding the spiral terminal can be done easily.Since the spiral terminal can be held easily, it can be fixed stably. Asno end of the spiral spring exists in the outer peripheral part,repeated connection with an electrode does not cause the substrate to beshaved by the end of the spiral spring, and therefore the reliability ishigh.

The spiral terminal of the present invention is a minute terminal, asshown in FIGS. 1(a) and 1(b), having an outer diameter D is equal to orless than 1 mm, the thickness b of the spiral spring 1 u is 100 μm-500μm, and the height c of the protrusion 1 t is 50 μm-200 μm, for example.The FIGS. 1(a) and 1(b) show an example in which the protrusion 1 t hasa neck; however, the present invention also includes an embodiment whichdoes not have a neck. FIGS. 1(a) and 1(b) show an example where a spiralterminal has an approximately circular cross-section when cut with aplane perpendicular to the longitudinal direction of the spiralterminal. However, the spiral terminal of the present invention is notlimited to such a circular shape: it may be an elliptical shape or acircular shape having a partly warped circumference, or a polygonalshape, such as triangle, square, etc. The polygonal shape may have sidesof different length, not limited to a regular polygon.

The FIGS. 2(a) and 2(b) show examples of columnar spiral springs havinga circular cross-section when cut with a plane perpendicular to alongitudinal direction of the spiral terminal. FIG. 2(a) is a sectionalview of a spiral terminal whose spiral spring consists of one arm. FIG.2(b) is a sectional view of a spiral terminal whose spiral springconsists of two arms. The present invention includes an embodiment inwhich the spiral spring has three or more arms. In the example of FIG.2(b), the tips of two arms are connected at the central part, wherein aprotrusion (not illustrated in the figure) exists. The modifiedembodiments of the spiral terminal of the present invention may have astructure such that a plurality of springs are arranged meandering fromthe outer peripheral part thereof to the center. The examples of suchstructure are shown in FIGS. 6(a)-6(d). This type of structure allowssignal electric currents to flow radially from the center, wherebymutual electromagnetic effects are offset, and accordingly satisfactoryhigh frequency characteristics can be obtained.

An example of an inspection socket equipped with spiral terminals of thepresent invention is shown in FIG. 3(d). As shown in FIG. 3(d), one pairof spiral terminals 31 a and 31 b, which are arranged with theirrespective protrusions face outward and a ring 39 interposed betweenthem, are engagedly put in each through-hole of an electricallyinsulative substrate 32. The ring 39 functions to secure a space for thespiral terminals 31 a and 31 b to perform a stroke, and thereby thespiral terminals are prevented from being in contact with each otherwhen they are transformed.

The socket for inspection equipment shown in FIG. 3(d) is used placedbetween a semiconductor 35 and a transformer 38 of measurementequipment. As a result of being put between the semiconductor 35 and thetransformer former 38, the socket connects with the electrode 36 ofsemiconductor 35 and the electrode 37 of transformer former 38 with amoderate contact load due to the additive force of the spiral spring.Thus, an electrical signal obtained from the semiconductor 35 is led tomeasurement equipment via the transformer former 38.

The spiral terminal of the present invention is useful as a spiralterminal of a socket for inspection equipment used in the inspection ofa semiconductor of land grid array arrangement, and the like. Likewise,the spiral terminal of the present invention is useful as a spiralterminal of a connector mounted in the land electrodes of communicationequipment such as a cellular phone or electronic equipment such as apersonal computer. The electrode of inspection equipment or electronicequipment is preferably plate-shaped in order to secure a sureconnection with a spiral terminal having a protrusion. However, anelectrode having an uneven or depressed surface can also be used.

(Method of Manufacturing a Spiral Terminal)

The manufacturing method of the present invention for the spiralterminal typically includes a step of forming a resist structure byX-ray lithography, a step of forming a layer consisting of metallicmaterial by electroforming in the resist structure so as to make acolumnar spring, a step of forming a resist structure by X-raylithography on the spring, and a step of forming a layer consisting ofmetallic material by electroforming in the resist structure so as tomake a protrusion protruding outward.

With such method, in which the spiral spring of a spiral terminal isproduced using X-rays and electroforming in combination, a high aspectratio can be attained as compared with a case of manufacture using amethod such as a lithography method using IW, a laser processing method,or a method using etching or punching. For example, spiral terminalshaving an aspect ratio (b/a) of 2 or more as shown in FIG. 1(a) caneasily be manufactured, and it is also possible to manufacture spiralterminals having a aspect ratio of 30 or more than. Since a high aspectratio is obtained, the stroke can be increased by designing the width aof the spring thinner and increasing the number of spirals. Also, thecontact load can be increased by increasing the thickness b of thespring. Therefore, spiral terminals exhibiting high connectionreliability can be manufactured.

More specifically, spiral terminals exhibiting a stroke of 100 μm ormore and a contact load of 0.03 N can be easily manufactured. Thecontact load can be made 0.1 N or more. Since the thickness b can beincreased even if the width a of the spring is thin, the spiral terminalcan achieve electrical continuity of a large electric current equal toor more than 0.5 A.

In the manufacturing method of the present invention, X-rays (wavelengthof 0.4 nm) which are shorter wavelength than UV (wavelength of 200 nm)are used because a spiral terminal having a high aspect ratio canthereby be obtained. In particular, synchrotron X rays (hereinafter,called “synchrotron radiation”) among the X-rays are preferably used inview of their high directivity. The LIGA (Lithographie GalvanoformungAbformung) process which uses synchrotron radiation is advantageousbecause deep lithography is possible with it, whereby it is possible toproduce metal microstructures having a height of several hundreds μmorder with precision of micron order and in large quantities.

If an attempt to manufacture a spiral terminal by machining process suchas curling up of a plate, there is a limit to miniaturization of thespiral terminal, and a possible smallest spiral terminal that can bemade by such machining process will have a thickness b of 1000 μm and adiameter D of about 500 μm-1000 μm. With this size, it is difficult tocomply with high density packaging of semiconductors. It is alsodifficult to manufacture precision spiral terminals in large quantities,precisely with satisfactory reproducibility.

According to the present invention, it is possible to comply with highdensity packaging of electronic equipment since spiral terminals havinga thickness b of 100 μm-500 μm and a diameter D of 100 μm-1000 μm caneasily be manufactured precisely with satisfactory reproducibility andin large quantities. Moreover, because of the manufacturing method inwhich lithography and electroforming are combined, the microstructurecan be formed integrally, the number of parts can be decreased, and thepart cost and assembling cost can be reduced.

Since the method uses lithography and electroforming in combination, theprotrusion at the center of the whirlpool in the spiral spring can beformed more easily with the method as compared with the method of makingconvex formation mechanically after forming the spiral spring, andaccordingly the productivity and the product yield are high. Moreover,since the protrusion can be formed precisely, it is possible to reducethe variation in the height of the terminal, and accordingly it ispossible to reduce the variations in the stroke and the contact load toabout {fraction (1/10)} as compared with those in the case of forming bymachining, and thereby the connection reliability can be enhanced.

In the manufacturing method of the present invention, a resin layer 42is formed on an electroconductive substrate 41 as shown in FIG. 4(a).The electroconductive substrate is, for example, a substrate made ofmetal such as copper, nickel, or stainless steel, or a silicon substrateto which a metallic material such as chrome or titanium is applied bysputtering. The resin layer is made of a resin material containingpolyester methacrylate such as polymethyl methacrylate (PMMA) as a maincomponent, or chemical amplification type polymer material havingsusceptibility to X-rays, or the like. The thickness of the resin layercan be optionally set according to the thickness of the spiral spring tobe formed; for example, it can be designed to be 100 μm-500 mm.

Next, a mask 43 is arranged on the resin material 42, and X-rays 44 areirradiated thereto through the mask 43. Preferably, the X-ray issynchrotron radiation. The mask 43 consists of a transparent substratematerial 43 b and an X-ray absorption layer 43 a formed according to thepattern of the spiral spring. The transparent substrate material 43 b ismade of silicon nitride, diamond, silicon, titanium or the like. TheX-ray absorber layer 43 a is made of a heavy metal such as gold,tungsten, or tantalum, or a compound thereof, or the like. A resin layerportion 42 a of the resin layer 42 is exposed to the irradiation ofX-rays 44, and its quality changes, but a resin layer portion 42 b isnot exposed because of the X-ray absorber layer 43 a. Therefore, onlythe part in which the quality has changed because of the X-rays 44 isremoved by the development and consequently a resist structure 42 b asshown in FIG. 4(b) is obtained.

Subsequently, a metallic material 45 is deposited by electroforming inthe resist structure 42 b as shown in FIG. 4(c). The electroformingmeans that a layer consisting of a metallic material is formed, using ametallic ion solution, on an electroconductive substrate. The metallicmaterial 45 can be deposited in the resist structure 42 b byelectroforming using the electroconductive substrate 41 as a cathodeelectrode. In a case where the metallic material is deposited to adegree in which the space of the resist structure is substantiallyburied, the spiral spring can be obtained from the accumulated metallicmaterial layer. In a case where the metallic material has been depositedin the resist structure beyond the height of the resist structure, ametal microstructure having a space is obtained by removing the resiststructure and the substrate. The metal microstructure thus obtained canbe used as a mold in the method of manufacturing a spiral terminalaccording to the present invention as described later. Nickel, copper ortheir alloy is used as the metallic material, and particularly nickel ora nickel alloy such as nickel manganese is preferable from the viewpointof enhancing the wear resistance of the spiral terminal.

After electroforming, the thickness is adjusted to a predeterminedmeasure by polishing or machining (FIG. 4(d)), and thereafter, forexample, a resin layer 46 made of negative resist is formed on thespiral spring (FIG. 4(e)). When UV47 or X-rays are irradiated through amask 48, the portion 46 b of the resin layer 46 is exposed and theportion 46 a of the resin layer 46 is not exposed (FIG. 4(f)).Therefore, a resist structure 46 b is produced by removing the otherpart by the development, leaving the part hardened due to UV or the like(FIG. 4(g)). The mask 48 may be a mask having the similar specificationas the mask 43.

Next, a layer consisting of metallic material is formed byelectroforming in the resist structure 46 b, and a protrusion 49 isgrown, protruding outward, by plating. The protrusion 49 has a contactsurface with a shape of a part of paraboloid of revolution as shown inFIG. 4(h), for contacting with an electrode. The protrusion having acontact surface which is a part of a spherical surface (not shown in thefigure) can also be formed. During electroforming, electric line offorce spreads in the space of the resist structure 46 b and theequivalent points thereof form a spherical surface or paraboloid ofrevolution, and accordingly a protrusion having a plating surface in ashape of a part of a spherical surface or part of paraboloid ofrevolution can easily be formed when the protrusion is grown by plating.

After formation of the protrusion 49, the resist structures 42 b and 46b are removed by wet etching or plasma etching as shown in FIG. 4(i).Subsequently, the electroconductive substrate 41 is removed by wetetching using acid or alkali, or by mechanical processing, andconsequently a spiral terminal of the present invention having acolumnar spiral spring 45 and a protrusion 49 can be obtained as shownin FIG. 4(j).

In order to enhance its electrical continuity, the spiral terminal thusobtained is preferably coated, by a barrel plating or the like, with aprecious metal, such as Au, Rh, Ag, Ru, Pt, or Pd, or an alloy of thesematerials, with a thickness of 0.05 μm-1 μm. Such coating layer can alsobe formed in the step (FIG. 4(i)) before the removal of a substrate.

FIGS. 3(a) to 3(d) show a method of manufacturing an inspection socketfrom spiral terminals. A connector to be mounted in electronic equipmentcan also be manufactured by a similar method. The method ofmanufacturing such an inspection socket or a connector for mounting isnot limited to the method illustrated in FIGS. 3(a) to 3(d). However,such method is advantageous in view of its ease for manufacturing.First, as shown in FIG. 3(a), through-holes are formed in anelectrically insulative substrate 32, at positions corresponding to thepositions of the electrode of a semiconductor to be inspected. Thediameter of the through holes is adjusted according to the outerdiameter of the spiral terminals to be accommodated therein.Subsequently, a lower-cover sheet 33, in which through holes are formedsimilarly at the positions corresponding to the arrangement of theelectrodes of the semiconductor, is attached to the substrate 32. Thediameter of the through holes of the lower-cover sheet is smaller thanthe outer diameter of the spiral terminals to be accommodated thereinsuch that the spiral terminals do not drop off the substrate.

Thereafter, a pair of spiral terminals 31 a and 31 b, which are arrangedwith their protrusions facing outward, and a ring 39 interposed betweenthe spiral terminals 31 a and 31 b are engagedly put in each of thethrough-holes of the substrate 32 as shown in FIG. 3(b). Subsequently,an upper-cover sheet 34 similar to the lower-cover sheet 33 is attachedto the substrate 32. Thus, an inspection socket according to the presentinvention is obtained as shown in FIG. 3(c). The material of thesubstrate 32, lower-cover sheet 33, and upper-cover sheet 34 may be anelectrically insulative material such as a polyimide resin or generalfiber reinforced plastic (FRP), for example.

A method of manufacturing a spiral terminal according to anotherembodiment of the present invention includes a step of forming a resiststructure with a metal mold and a step of forming a layer consisting ofmetallic material in the resist structure by electroforming, therebyproducing a columnar spring, and a step of forming a layer consisting ofmetallic material in the resist structure by electroforming so as toproduce a protrusion protruding outward. With such method also, as inthe case of the above-mentioned manufacturing method in which a minutespiral spring is formed by X-ray lithography, it is possible tofabricate a minute terminal precisely with a satisfactoryreproducibility. The spiral terminal thus fabricated has a high aspectratio and accordingly a protrusion at the center thereof can be formedprecisely. Consequently, the contact reliability thereof is high.Moreover, the method is advantageous in that a mass production of spiralterminals is possible using the same mold.

First, as shown in FIG. 5(a), a depressed resist structure 52 as shownin FIG. 5(b) is formed by press or injection molding or the like using amold 50 having a protruding portion. Thermoplastic resins, includingacrylic resins such as polymethyl methacrylate, polyurethane resin, orpolyacetal resin such as polyoxymethylene, are used as the material ofthe resist structure. As for the mold 50, since it is a metalmicrostructure similar to the spiral terminal of the present invention,it is formed preferably by the above-mentioned method, in which an X-raylithography method and electroforming are combined.

Next, after reversing the top and the bottom of the resist structure 52,it is attached on the electroconductive substrate 51 as shown in FIG.5(c). Subsequently, the resist structure 52 is polished to form a resiststructure 52 b as shown in FIG. 5(d). The subsequent steps are the sameas described above: a metallic material 55 is deposited in the resiststructure 52 b by electroforming (FIG. 5(e)), the thickness is adjustedby polishing or grinding (FIG. 5(f)), a resin layer 56 is formed (FIG.5(g)), and UV 57 or X-rays are irradiated thereto through a mask 58. Ofthe resin layer 56, a resin layer portion 56 b is exposed but a resinlayer portion 56 a is not exposed (FIG. 5(h)). Therefore, a resiststructure 56 b can be produced by removing the other part bydevelopment, leaving the part hardened by UV or the like (FIG. 5(i)).

Subsequently, a protrusion 59 having a contact surface to contact withan electrode is formed by electroforming and plating. As shown in FIG.5(j), the contact surface has a shape equivalent to a part of paraboloidof revolution or the like. After formation of the protrusion 59, theresist structures 52 b and 56 b are removed (FIG. 5(k)), and theelectroconductive substrate 51 is removed. Thus, the spiral terminal ofthe present invention having a columnar spiral spring 55 and aprotrusion 59 can be produced (FIG. 5(l)). The spiral terminal ispreferably provided with a coating layer made of Au, Rh, or alloythereof, or the like.

EXAMPLE 1

First, a resin layer 42 was formed on an electroconductive substrate 41as shown in FIG. 4(a). A silicon substrate to which titanium is appliedby sputtering was used as the electroconductive substrate. The materialfor forming a resin layer was a copolymer of methyl methacrylate andmethacrylic acid, and the thickness of the resin layer was 200 μm.

Next, a mask 43 was arranged on the resin layer 42, and X-rays 44 wereirradiated through the mask 43. As for the X-rays, synchrotron radiationby SR equipment (NIJI-III) was adopted. The mask 43 had an X-rayabsorber layer 43 a, which was formed on a transparent substratematerial 43 b corresponding to the pattern of the spiral terminal. Thetransparent substrate material 43 b of the mask 43 was consisted ofsilicon nitride, and the X-ray absorber layer 43 a was made of tungstennitride.

After the irradiation of X-rays 44, development was performed by methylisobutyl ketone, and the part 42 a in which the quality has been changedby the X-rays 44 was removed. As a result, a resist structure 42 b asshown in FIG. 4(b) was obtained. Then, as shown in FIG. 4(c), a metallicmaterial 45 was deposited by electroforming in the space of the resiststructure 42 b. Nickel was used as the metallic material. After theelectroforming was completed, the unevenness of the surface waseliminated by polishing so as to have a uniform thickness as shown inFIG. 4(d), and a resin layer 46 was formed on the spiral spring (FIG.4(e)). Thereafter, UV 47 was irradiated through the mask 48 (FIG. 4(f).The resin layer 46 was a UV resist (SU-8 made by Microchem Corp.), andthe thickness of the resin layer 46 was 50 μm. The mask 48 was agenerally available photomask. Subsequently, the part other than theportion hardened by the UV irradiation was removed by development, andthe resist structure 46 b having a hole at the center of the spiral(FIG. 4(g)).

Subsequently, electroforming was performed, and the protrusion 49protruding outward was formed by growing a plating metal to the heightof 50 μm from the top surface of the resist structure 46 b (FIG. 4(h)).After the formation of the protrusion 49, the resist structures 42 b and46 b were removed by plasma etching as shown in FIG. 4(i). Subsequently,the electroconductive substrate 41 was separated, by a mechanicalmethod, from the spiral terminal having the protrusion. Thereafter, acoating layer (not shown in the figure) consisting of gold was formedwith a thickness of 0.1 μm by barrel plating. The separation of thespiral terminal from the substrate may be accomplished by etching theelectroconductive substrate. The total height of the protrusion formedon the spiral spring was 100 μm.

The spiral terminal thus obtained is shown in FIGS. 1(a) and 1(b). Thespiral terminal had a columnar spiral spring 1 u and a protrusion 1 tprotruding outward at the center 1 uc of the spiral of the spiral spring1 u. The protrusion had a contact surface 1 tc for contacting with anelectrode, and the shape of contact surface 1 tc was a part ofparaboloid of revolution. The outer peripheral part 1 ug of the spiralspring 1 u has a hollow ring structure. The diameter D was 480 μm andthe thickness b of the spiral spring was 150 μm. The width a of thespring was 10 μm, and the aspect ratio (b/a) was 15. The number ofspirals was 3.3 turns, and the stroke of the spring was 100 μm. Thespiral spring had a protrusion with a neck at the center thereof and theheight c was 100 μm.

Subsequently, as shown in FIG. 3(a), the lower-cover sheet 33 and thesubstrate 32, both of which had through-holes at the positionscorresponding to the positions of the electrodes of a semiconductor tobe inspected, were attached together. The substrate 32 was made of apolyimide resin and had the thickness of 500 μm, and through-holeshaving a diameter of 500 μm were formed therein. Also, the lower-coversheet 33 was made of a polyimide resin, and had the thickness of 20 μm,in which holes having a diameter of 400 μm were formed at the positionscorresponding to the positions of the through-holes of the substrate 32.

Next, as shown in FIG. 3(b), the spiral terminals 31 a and 31 b werearranged with their respective protrusions facing outward and the hollowring 39 having an outer diameter of 480 μm and a height of 200 μm wasinterposed therebetween. Thus, they were engaged in each through-hole ofthe substrate 32, and an upper-cover sheet 34 similar to the lower-coversheet 33 was attached to the substrate 32, whereby an inspection socketof the present invention was produced as shown in FIG. 3(c).

As shown in FIG. 3(d), the inspection socket thus obtained was mountedon the electrodes 37 of the transformer former 38 of inspectionequipment, and a semiconductor 35 to be inspected was placed on theinspection equipment. When a pressure of 70 mN force was applied in thisstate in the direction indicated by the arrows, electrical continuitywas attained between the plate-shaped electrodes 36 of the semiconductor35 and the electrodes 37 on the transformer former 38 because of theadditive force of the spiral spring. Thus, the inspection of thesemiconductor could be accomplished based on electrical signals obtainedin this manner.

In this example, the diameter D of the spiral terminal was 480 μm.However, it was found that spiral terminals having a diameter D of about100 μm can be produced according to the manufacturing method of thepresent invention, and that such spiral terminals can comply with thehigh density packaging of electronic equipment.

It should be noted that the embodiments and the examples disclosed inthis specification are exemplary in all respects and that the presentinvention is not limited to them. It is intended that the scope of thepresent invention be shown by the claims rather than the description setforth above and include all modifications and equivalents to the claims.

According to the present invention, it is possible to provide inspectionsockets and connectors for mounting, both having spiral terminalsexhibiting high connection reliability.

1. A minute spiral terminal for attaining electrical continuity with anelectrode of electronic equipment or inspection equipment, the spiralterminal comprising a columnar spiral spring and a protrusion protrudingoutward at the center of the spiral of the spiral spring, the protrusionhaving a contact surface to be in contact with the electrode, the shapeof the contact surface being a part of a spherical surface or a part ofparaboloid of revolution.
 2. A spiral terminal according to claim 1,wherein the outer peripheral part of the columnar spiral spring has ahollow ring structure.
 3. A spiral terminal according to claim 1,wherein the spiral terminal is made of nickel or nickel alloy.
 4. Aspiral terminal according to claim 1, wherein the spiral terminalfurther comprises a coating layer consisting of a precious metal oralloy of a precious metal.
 5. A method of manufacturing a spiralterminal set forth in claim 1, wherein the method comprises the stepsof: forming a resist structure by X-ray lithography; forming a layerconsisting of metallic material in the resist structure by means ofelectroforming so as to form a columnar spiral spring; forming a resiststructure on the spiral spring by lithography; and forming a layerconsisting of metallic material in the resist structure byelectroforming in order to form a protrusion protruding outward.
 6. Amethod of manufacturing a spiral terminal set forth in claim 1, whereinthe method comprises the steps of forming a resist structure by a metalmold; forming a layer consisting of metallic material in the resiststructure by means of electroforming so as to form a columnar spiralspring; forming a resist structure on the spiral spring by lithography;and forming a layer consisting of metallic material in the resiststructure by electroforming in order to form a protrusion protrudingoutward.
 7. A socket equipped with the spiral terminals defined in claim1, wherein the socket is used for the inspection of semiconductors ofland grid array arrangement.
 8. Inspection equipment having a socketdefined in claim
 7. 9. A method of inspecting a semiconductor, themethod using a socket defined in claim
 7. 10. A connector having spiralterminals defined in claim 1, wherein the connector is connected with aland electrode.
 11. Electronic equipment having a connector set forth inclaim 10.